In general, a method of cooking food contained within a cooker is largely divided into a direct-heating type in which the food is directly heated using a heat source such as a gas range, a burner or the like, and an indirect-heating type in which the food is indirectly heated using a heat source such as water vapor or steam. Specifically, an example of the indirect-heating method includes a method in which superheated steam is injected into the cooker to cook the food.
Such a cooking method using the superheated steam features that food is heated uniformly to cause the food to be prevented from being burnt locally and the temperature and supply amount of the superheated steam to be easily adjusted, thereby readily controlling the characteristics of the cooking and preventing the occurrence of oxidization due to steam which causes flavor to be maintained.
Cooking equipment using the superheated steam includes a cooking room, a steam generator for heating water supplied thereto from a water tank to generate steam, a superheated steam generator for heating the steam generated from the steam generator to generate superheated steam, and a steam piping unit for supplying the superheated steam generated from the superheated steam generator to the cooking room.
However, the superheated steam generator entails several problems in that since it should have a plurality of constituent parts including a screw-type heat transfer tubes to secure a fluid-passing cross-section required to generate and treat the superheated steam, the operating structure thereof is complicated and the manufacturing cost increases, which leads to an increase in maintenance and repair costs of products.
In addition, the superheated steam generator has a problem in that it is difficult to obtain superheated steam having a uniform temperature since a deviation of fluid flow rate is large due to a complexity of built-in components. Moreover, if local overheat occurs in the heat transfer tube itself due to the deviation of fluid flow rate, there is caused another problem in that the built-in components are deteriorated to thereby degrade durability of the superheated steam.